The present invention relates to map data for on-road vehicles, such as automobiles, trucks, and buses, and in particular to map data that supports advanced driver assistance systems for such on-road vehicles.
Advanced driver assistance systems (“ADAS systems”) have been developed to improve the comfort, convenience, efficiency, and overall satisfaction of driving. Examples of advanced driver assistance systems include adaptive headlight aiming, curve warning, adaptive cruise control, and adaptive shift control, as well as others. Some of these advanced driver assistance systems use sensor mechanisms in the vehicle, such as radar and vision-oriented sensors (e.g., cameras), to determine the current state of the vehicle and the roadway around the vehicle.
Some advanced driver assistance systems use digital map data to provide information about the road network, road geometry, road conditions and other features associated with the road network around the vehicle. Digital map data is not affected by environmental conditions, such as fog, rain or snow. In addition, digital map data can provide useful information, such as speed limits, traffic and lane restrictions, etc., that cannot reliably be obtained by cameras or radar. Further, digital map data can be used to determine the road ahead of the vehicle even around corners or beyond obstructions. Accordingly, digital map data can be a useful addition for some advanced driver assistance systems.
For some advanced driver assistance system applications, it is useful to have a relatively accurate representation of road shape properties, such as curvature and heading. Prior map database representations of roads include data that indicates the positions of the roads from which curvature and heading can be derived. However, using prior map database representations of roads to obtain curvature or heading data can produce irregularities under certain circumstances.
Accordingly, there exists a need for a way to reliably and accurately represent the curvature or heading of roads in a map database.